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Fasten toilet to existing hydronic floor slab

oldguy Member Posts: 1
I'm a home re-modeler. My question is seeking a method to secure a toilet (vitreous china) to a concrete floor (with existing hydroponic radiant heating). Like some super adhesive that bonds well to a (vitreous china) toilet and concrete without drilling into the radiant heated concrete slab.  

We're installing a new bathroom in a basement with existing hydroponic floor (basement slab below grade). So we obviously do not want to drill into the concrete floor with fasteners. Because it's a basement below grade the plumber is installing a rear discharge pump-up toilet. Normally a toilet (rear discharge or normal bottom discharge) is bolted to the floor using metal Johnni bolts (bolts would be secured by drilling holes into concrete floor). Since the weight is always downward, the toilets most likely movement would be lateral.

I called he manufacturer (SANIFLO) and asked for an alternative method to secure a toilet to the floor and he (the installation technical expert) gave me the only answer he knows- silicone.

My question from a hydponic radiant (concrete) perspective - is silicone the best product available for bonding vitreous china to concrete? I read on this website that silicone has its limits for bonding marble like materials.

Thanks for any advise or experience of previous installers.


  • kcopp
    kcopp Member Posts: 4,262

    How was the tubing installed? Was it staped to foam on the bottom of the slab? even if it was done w/ mesh and pulled up if you only drill 1" down you should be fine.
  • Paul48
    Paul48 Member Posts: 4,469

    You are planning on putting the toilet on the concrete?No tile? I'd have no problem using silicone if it was on tile, not concrete.
  • icesailor
    icesailor Member Posts: 7,265
    Poor planning:

    Whomever laid out the tubing should have laid out the tubing so it wasn't directly underneath the toilet. For this reason. The toilet you describe should use a normal toilet closet flange, firmly screwed into the wall with backing.  The flange should be set as it it was on a floor. The closet bolts through the flange are what holds the bowl in place. The ones in the floor are only to give some side to side support. Under normal use, it shouldn't't have any side to side force. The only place where it is a concern is in a public restroom for women. Some will never allow their skin where any other strange body has been before and they will stand on the toilet seat to go. Some may notice toilet seats all scratched up if it is a narrow stall. They need the narrow stall so they won't tip over while standing on the seat.

    If the heat is running, get the floor tubes hot and mark out the tubes with a infra-red heat gun. Then, drill a nut-sert into the slab or Epoxy one in. It's the flange mounted on the wall that counts. And whatever one does, DO NOT use a wax ring. Use a rubber one. The bowl wax ring will leak. Use the black rubber rings.

    That's my experience.
  • icesailor
    icesailor Member Posts: 7,265
    Silicone Sealant:

    Silicone is a great product to put on the floor and glue the bowl down. What is better is the water based products like Phenoseal. It glues the bowl down and if you ever need to take up the bowl, you need to put a wedge tool between the floor and bowl. It will either pull up the tile or break the bowl. I see the same in public rest rooms with urinals on the wall. Try to get one of those suckers off the tile wall without breaking it or getting it back in the exact same location.

    You shouldn't need to use anything under it like Silicone unless the floor is so crooked that it looks like a rutted road.

    But that's my opinion.
  • kcopp
    kcopp Member Posts: 4,262

    toilets don't use a flange to hook it to the wall... you need to use a fernco-like connector to lead it to the macerating box.
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